Barnfield on Rail Volume

" When it comes to a board having a good or bad "feel", one of the primary components is the amount of foam contained in the rail.  The overall thickness of the board down the center is important, but how that thickness is carried out to the rail is absolutly crucial to performance.  Among top surfers various rail volumes suit each one's style a bit differantly.  For example, Bobby Owens at 140 pounds prefers a very, very slender rail with as little volume as possible.  On the other hand, Shaun Tomson at 175 pounds prefers a rail of substantial volume and fullness.  While there is a signifcant differance in their body weights, the actual center thickness of their boards varies by less than would be expected.  This indicates that a board's center thickness is less important to them than rail volume is, and rightly so.  The way a board rides is much more dependent on rail volume than overall center thickness.  The effects of this are felt primarily during the weighting(sinking) and unweighting(releasing) of the board throughout the turning process.  The actual shape of the rail area can come in many differant forms, many of which have several differant volumes and will feel quite comprable to one another during weighting and unweighting.  Among good surfers I find that we rarely talk about the actual shape of the rail, all our time is invested in getting the volume correct.  I will be the first to acknowledge that rail shape is an important aesthetic feature in an attractively built board, but its worth in the area of function, though respectable, is often over-emphasized.  The rail volume as it compares to an unchanged center thickness is affected by two main factors; one, the amount of vee in the bottom, and two, the amount of dome on the deck.  If you have alot of vee and a very domed deck the rail will always be thinner than the center thickness.  You can form  that rail into various shapes, but its volume cannot be increased.  To increase its volume you will need a flatter deck or bottom so that the available thickness can be carried out to the rail area.  Once you have determined a starting thickness for your boards you can begin trying differan board shapes to arrive at the board volume most appropriate for your style.  I suggest you make most of the changes to the rail volume from the deck since you need to secure a bottom shape that is workable for your needs and once you find it you won't want to be changing it too much.  The extreme results of a very domed deck or a very flat deck are rails either so sloped and thin or so full and boxy that very little can be done with them to refine their shapes.  Rail volume and shape are probably the most difficult areas of a boards shape to consistently arrive at, even for the expereinced shaper.  While other areas of a board's shape can be measured in some simple manner, the rail area can only be felt and eyed until the proper shape is gained.  This is a highly error ridden method for acheiving something so important.  The differance between the size of your hands, or the fact that one of them has been holding the planer all day can grossly effect their ability to feel accurately.  Anyone who has experience in the field of Industrial Design knows how easy the eye's perception of a form can be altered by numerous factors."    Article by Bill Barnfield -------- Surfing Magazine May 1985,  Volume 21, Number 5  

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Borrowed this from Surfing Mag.  Would have posted it under the numerous threads that Bill has contributed to concerning rails, rail marking etc.  But This kind of thought and insight into design theory is "Stand Alone" . Thought it would be of interest to all and most especially the author,  as it may have been awhile since he has reveiwed this series of design articles that he did for "Surfing" in the "80's.  All of these articles are a good read and though some things have changed as surfboard design has progressed, many things remain the same.  Would have posted this a couple of nights ago, but I'll be darned if I dldn't get down to the last word, hit the wrong button and lost the whole draft.  Using my laptop and don't have a scanner or I would have attemtped to do it the easy way.  Now that you know the effort it took, please forgive the typos etc.  For your reading and thought provoking pleasure   Lowel

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Thx, that was a gem.

Very Appreciated! 

Amazing contrast between the depth of thought in this article, and the superficial treatment that the magazines print today.

Yeah , thanks for that , a great read.

That’s a nice case Bill puts forward for using rail templates , too.

Great writing, reflecting deep thinking… from a generation ago?! And today, we’re still thinking about the same things! It’s suprising how many sufers don’t distinguish rail shape from volume, and their almost independent effects on performance. Here’s something I wrote not too long ago, that might suggest a different way to see things…

"…

even

small changes in rail shape and volume can have dramatic effects on how a board
performs, and something like a miscalculation in volume, or a misplaced edge,
can ultimately become a “make or break” design element in what would otherwise
be a finely tuned surf craft.

It is helpful to view rail shapes on a continuum, from hard – having a distinct, hard turn or corner at the bottom of the rail, either created by the shape of the rail, or a bead of resin that is carefully sanded to a sharp edge along the bottom of the rail (or both), to soft – completely rounded, having no edge or corner at all. These two extremes are at the ends of the spectrum for most modern rail shapes, and in the middle there is an infinite continuum of shapes and combinations of shapes that gives the designer/shaper a lot of ideas to play with. To clarify, a rail’s shape can be hard or soft, just as a rail’s edge can be hard or soft – confusing terminology. But it should be understood that a rail can either be hard or soft, depending on it’s shape, and may or may not have an edge… and that edge may be hard or soft itself.

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And in

addition to hard or soft rail shapes, and hard or soft edges, there is also the
matter of rail volume, which becomes another determining factor in a rail’s
overall shape and performance.

 

Later...

"Rail

shapes are not only modified by the location of the apex, but also by their
volume. While changing the volume of the rail alone without changing the rail’s
shape can be accomplished by simply scaling an existing shape down to the
desired volume, a shaper can manipulate both volume and shape using a variety
of basic, tried and true rail designs. “Egg” rails, “pinched” rails, and
“knife” rails are three commonly used terms to describe a sequence of rail
profiles that effectively reduce volume and manipulate release without the use
of hard edges.

 

And later...

 

" For the most part, the foil

of the rail – its change in volume as you go nose to tail – should be smooth to
minimize turbulent drag and create the feeling of balance and predictability
for the rider. Abrupt shape or volume changes along the rail greatly increase
drag as the laminar flow along the rail is disrupted and deflected. Viewed from
the side, the thickness of the rail should flow, gradually thicker, then
gradually thinner, without noticeable transitions between changes in rail
volume, apex location, edge, etc., except for the deliberate introduction of
bumps, wings or the like, as discussed earlier.

 

The modern performance shortboard rail is a perfect example of how different rail profiles can be combined along different lengths of rail to achieve a very complex final result that allows the rider to use different sections of rail for different purposes at different times. Particular attention should be paid to the smooth, seamless, nearly unnoticeable transitions between rail profiles as the rail is dissected from tail to nose. This is perhaps one of the greatest tests of a master shaper – the ability to blend dynamic contours that are sometimes very different from one another into a graceful combination of design features that all fit seamlessly together.

 

Sorry for the messy formatting...

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Very interesting… if you want to quantify that, what part of a cross section should arbitrary be considered as the rail ? 2 inches from the apex towards the center? Let’s say I want to compare the volume of 2 different rails in the middle of a board, I have to compare the surface taken by the rails on each cross section, are there any proven method to put numbers on that variable? With such numbers, it would in theory be possible to test different rail shapes with same volumes to isolate variables. My understanding is that it would be best to know which rail volume suits you best before tweaking rail shape around that volume as the first factor has more impact then the latter.

You can compare rail volumes by either making a mold of the rail that’s a specific length, and filling it with liquid, and measuring the liquid, or the opposite… make a mold of the rail, fill the mold with pour foam, cut a specific length of that foam, then measure the volume of liquid it displaces when submerged. A less accurate way is to measure the circumference of the rail to a specific distance in from the apex. Longer circumferences mean greater volume.

I saw two things in this article that I realized almost immediatly;  one,  The new blanks that are available today both Poly and EPS (due to their consistent densities) allow one to easily adjust rail volume from the deck.  The norm with a Clark blank was to take it down to desired thichness from the bottom and to avoid cutting to deep into the deck. Cutting too deep into a Clark deck meant a soft deck.  On todays' blanks if the deck is too domed one can safely bring it down to blend it.  As Bill suggested changes in rail volume can be made from the deck and with today's consistent blanks there is no sacrifice to deck strength.  Two,  The other thing is the commonplace "beaked nose" of the 70's and early '80's.  Certainly thinning out and rockering the nose as done in modern shortboards has also allowed shapers to alter rail volume in the front third of the blank.  Like I said somethings have progressed but, alot of things remain the same.  Lowel 

I like using this tool. I record my favorite reference and use it to make new ones, with or without volume adjustment. The last one I made I added 1/16" more volume. Imo, deck roll, although related, is another design element. 

Good article by BB!

 

Good way to compare profiles, but does not measure volume easily. Also, the two rail profiles you show have different shapes and volumes. What was mentioned earlier was changing volume without shape - just scaling up the profile.

[quote="$1"]

Good way to compare profiles, but does not measure volume easily. Also, the two rail profiles you show have different shapes and volumes. What was mentioned earlier was changing volume without shape - just scaling up the profile.

[/quote]

Ok got it. I can do all that too.

I took that pic years ago, of two different unrelated boards, both boards work great for me.

My only point was to offer a simple cheap tool that eliminates some of the guesswork.

YMMV.

I’ve been on the software guys for years to produce a “longitutinal slice”.  All software has capacity to cut boards across the stringer (and it’s easy 9though not emotionally) to slice a board up that way to get rail profiles).  The thing hat amazes me about these profiles is how quickly the rail shape changes over say a 1" thick slice of a board.  Doesn’t seem that it should be much, but when you’re handling a block of foam you sure feel it.

A longitudinal slice is needed to get rid of the bunny ears you see in so many machine cut boards, where the software does not merge slices as smoothly as the designer envisioned.  Longitudinal slices would also permit accurate foiling of the rails front to rear (what NJ refers to in the middle of his post above).  I personally believe that rail foiling should provide lift and drive (like a fin) when the board is on rail. 

Watch vids carefully and you can see the nose of many board rising and falling through bottom turns as the rail foiling pops it out the water and the surfer counteracts to keep his line.  I’ve moved my rail thick point forward to change the foiling characteristics.  It’s tricky moving rail thick point forward of rocker thick point.  Keeping rocker thickness the same over the middle 1/3 of the board helps a bit with this.

 

PS this post shows the other thing that’s changed since Bill’s excellent article above (thanks for posting!) - machineheads have got into it and are trying to get the ideas to come out of zeros and ones rather than Skils (pun intended)

Good way to compare profiles, but does not measure volume easily.

[quote="$1"]

You can compare rail volumes by either making a mold of the rail that's a specific length, and filling it with liquid, and measuring the liquid, or the opposite... make a mold of the rail, fill the mold with pour foam, cut a specific length of that foam, then measure the volume of liquid it displaces when submerged. [/quote]

Ok, so I didnt read everything before I posted the photo (I'm sorta busy).

But how is that measuring rail volume EASILY?

Are you serious about those measurement methods?

Have you really done that, honestly?

Red_Boards post makes a lot of sense. 

Where the thickest part of the rail foil is shaped helps determine the fulcrum on which the board pivots when on rail.  It can also help determine the overall turning radius... thickest part forward = more rail in the water/longer turning radius.  Thickest part aft = less rail in the water/shorter turning radius.  

On most of my really long longboards I shape the thickest part slightly aft of center to reduce the amount of rail in the water.

A sure fire volume measurement can be accomplished in a rectangular water tank.  Measure water level, sink board and measure the rise of the water.  Multiply water rise by length X width of tank to determine the exact volume of the board

Rail volume?  Most boards have a dome deck to a greater or lesser degree that would have to be taken in to account.  The problem with trying to determine rail volume is determining exactly where the deck and bottom end and the rails begin... I.E. 2" in from the edge?  4" in from the edge? 

hi nj, 

we’re lucky in this respect only because the internet gives us the opportunity to consolidate and add to what’s been documented previously.

if pioneering foam shapers & HWS builders had this technology in their day, consolidating and passing on to everyone here all their accumulated shaping expertise, we’d probably be thinking about… more and more of the same things! hehe " ) 

great thread btw

I think http://www.witchcraft.nu custom software uses longitudional curves for creating the foil, no crossections. However I would think that would be hard to edit. Showing a longitudinal slice on the other hand is relatively easy and something I could incorporate.

That was exactly my question. You can either consider the rail volume to extend to the limits of your rail replicating tool or use an arbitrary distance from the apex or a not so arbitrary way of determining this limit… I would even guess that the distance from the apex could change along the board, being much shorter towards the front and back ends of a board (like the line created by a continuous tucked under edge). That would mean a rail could be defined as the first x percents of the width at any given point as a reference. Or the rail could be defined as the part of the board that is outside the flat or almost flat panel made by the bottom of the board, but that distance looks short to me to define rail volume, as a lot more goes into the water when engaging the rails.

Do you attribute this only to rail foil? To me it looks like there are several design elements fighting each other, but it’s hard to tell (for me anyway) if it’s the rocker that wants to turn at one radius while fins want to trun at another radius or some other element. Sometimes on vids the wobble and bump looks so bad that it’s amazing the surfer manages to control it.

If the good people at swaylocks can figure out a way to describe what is rail and what’s not (and possibly an industry standard for measuring rail thickness (instead of thick, medium, thin…)), I’ll gladly add the volume calculations for the rail to boardcad.